Creation of this applet was inspired by a [url=https://twitter.com/solvemymaths/status/833212994725228545]tweet[/url] from [url=https://twitter.com/solvemymaths]Ed Southall[/url]. [br][br]Feel free to move any one (or more) of the white points. [br]You can adjust the sizes of the squares using the sliders. [br][br][color=#38761d][b]How does this applet informally illustrate that the areas of the 2 green triangles are equal? [/b][/color][br][br][b][color=#0000ff]How can you formally prove what this applet informally illustrates? [/color][/b]